The present invention is directed to a railroad roadway, particularly for rail-mounted vehicles operating at high speeds, and includes a track grating made up of rails and concrete ties with the ties partially embedded in a steel reinforced concrete slab. The concrete slab is reinforced in the longitudinal and transverse directions of the rails and the slab is poured in place on a continuous concrete substructure or base deposited on a subgrade with a separating layer between the concrete slab and the substructure.
In railroad roadways, the usual construction of a track still utilizes transverse ties supported on a ballast bed. This form of track construction, however, involves steadily increasing costs for maintenance, primarily for cleaning and compressing the ballast bed, especially where trains travel at very high speeds and have high axle loads. In contrast, the maintenance costs for rails, rail fastenings, and ties, particularly prestressed concrete ties, is small.
As an alternative to the use of ballast in a railroad roadway, it has been known to place the rails on continuous longitudinal girders, on gratings made up of longitudinal and transverse girders, or on continuous steel reinforced concrete slabs for transmitting loads into the subgrade as uniformly as possible. In poured-in-place slabs o gratings using steel reinforced concrete, the exact positioning of the rail fastenings poses difficulties. In addition, cracks resulting from deformation due to temperature cannot be avoided in continuous slabs and, in addition, the removal of surface water and cleaning of the slabs causes problems. Furthermore, the generation of noise is disproportionately greater in continuous slabs than in a railroad roadway employing ballast.
Another alternative to a railroad roadway using ballast is a known type of construction involving a steel reinforced concrete slab poured in place with steel reinforced concrete ties incorporated as track holding elements, note DE-C "Der Eisenbahningenieur" (Railroad Engineer), 38, 1987, Volume 7, pp. 347 to 353. By embedding prestressed concrete ties in the steel reinforced concrete slab, the rail fastenings in the ties are not effected by cracks in the slabs, as is the case when the rails are fastened directly to the steel reinforced concrete slabs. Instead, the unavoidable formation of free cracks in the steel reinforced concrete slab occurs in the form of finely distributed and harmless cracks along the flanks or sides of the ties. To construct such a railroad roadway, a track grating made up of ties and rails is first prepared for a predetermined length and is aligned and adjusted on a subgrade. The concrete for the slab is then poured and compacted with the concrete extending for a large part of the height of the ties and thus forming a bed for the ties. Accordingly, such a railroad roadway construction has good adaptability to different curves and different elevations of the rails in curved tracks. Its design differs depending on its application on a subgrade or in a tunnel.
In the construction of this load-bearing system on a subgrade, as is customary on open rail lines, a gravel base, approximately 20 cm thick and hydraulically set, forms a substructure placed on a frost-protection layer consisting of gravel. The supporting slab, positioned on the substructure with an intermediate layer of asphalt paint acting as a separating layer in the event a height adjustment is required, is constructed of poured-in-place concrete with a height dimension of 14 cm under the ties and an additional 12.5 cm height in the spaces between the ties. As a result, the slab has an over-all height or thickness of 26.5 cm The part of the supporting slab located below the ties includes a layer of crossing reinforcement. The concrete in the spaces between the sleepers is connected with the lower part of the slab by means of stirrups, and longitudinal reinforcement and transverse reinforcement in the form of reinforcing bars extends through holes in the ties. Such a supporting slab is poured in a number of layers and has a pronounced load distributing effect whereby the bending resistance of the slab has a pronounced significance in relation to the substructure.
In similar supporting systems for railways in tunnels, the tunnel floor constructed of steel reinforced concrete is available as an effective bearing foundation, so that the height of the poured-in-place concrete layer under the tie can be reduced to a minimum amount of 5 cm required for pouring the concrete. In this arrangement, only longitudinally reinforcement is used consisting of reinforcing bars extending through holes in the ties. Further, in such an arrangement, it has been suggested to position sound absorbing material on and next to the fixed roadway for absorbing airborne noise. Due to the considerable thickness of the supporting slab, especially in the region between the ties, the layer of such material can only be very thin and, as a result, it is not very effective.